A work machine may be used to move heavy loads, such as earth, construction material, and/or debris, and may include, for example, a wheel loader, an excavator, a front shovel, a bulldozer, a backhoe, and a telehandler. The work machine may utilize a work implement to move the heavy loads. The work implement of the work machine may be powered by a hydraulic system that may use pressurized fluid to actuate a hydraulic actuator to move the work implement.
During operation of the work machine, the implement may be raised to an elevated position. As the implement may be relatively heavy, the implement may gain potential energy when raised to the elevated position. As the implement is released from the elevated position, this potential energy may be converted to heat when pressurized hydraulic fluid is forced out of the hydraulic actuator and is throttled across a valve and returned to a tank. Typically, the conversion of potential energy into heat may result in an undesired heating of the discharged hydraulic fluid, which may require that the work machine possess additional cooling capacity. Recovering that lost or wasted potential energy for reuse may improve work machine efficiency.
One system designed to recover or recycle the energy associated with lowering a load is disclosed in U.S. Pat. No. 6,584,769 to Bruun (“Bruun”). Bruun discloses a hydraulic circuit including a hydraulic machine, the flow of which can be routed to the rod end of a double acting hydraulic cylinder. The hydraulic circuit also includes a variable hydraulic machine, a servo pump, and an accumulator. During operation, pressurized oil in the accumulator flows through a bi-directional pump of the variable hydraulic machine, which then conveys the oil to the lifting cylinder. In the event of a lowering movement, the direction of flow in the bi-directional pump is changed and oil is supplied to the accumulator. A disadvantage associated with the hydraulic circuit in Bruun is that it requires a bi-directional pump and a servo pump to perform the functions of extending and retracting the double acting hydraulic cylinder and recovering or recycling the energy resulting from the lowered load. The use of these components increases the complexity, size, and cost of the hydraulic circuit in Bruun.
The system of the present disclosure is directed towards overcoming one or more of the constraints set forth above.